The present invention relates to a tire, and more particularly to the sidewalls and beads of such a tire. French Patents FR 2 699 121 and FR 2 716 645 describe a tire having a radial carcass reinforcement of low H/S ratio, H being the height of the tire on its rim and S the maximum axial width thereof, which is intended to be mounted on a rim, at least one seat of which is inclined towards the outside and extended axially to the outside by a protrusion of low height. Said tire comprises at least one bead having the following characteristics:                a) the meridian profile of the center section of the carcass reinforcement is tangent to the anchoring bead wire of the carcass reinforcement at a point T such that the tangent TT′ forms with a line parallel to the axis of rotation of the tire an angle φ, which is open radially and axially towards the outside, of at least 70°,        b) the bead is intended to be mounted on a rim such as described in the above patents, that is to say, one having the special characteristic of having at least one rim seat inclined towards the outside, said seat being extended axially to the inside either by a rim flange or by the rim base on which is laid a tread bearing support, a lateral face of said support being used as the rim flange, and said seat being extended axially to the outside by a protrusion or hump of low height;        c) the external contour of the bead has a profile adapted to the profile of the mounting rim above, and said bead has the special feature of having a heel arranged axially to the inside, whereas the bead toe is arranged axially to the outside.        
When the axially outer wall of said bead is set back axially relative to the axially outermost end of the rim, the type of tire described does not protect the axially outermost metallic elements of the rim against curbing aggression when traveling in towns. This problem may be solved by adapting the axially outer form of the toe of the bead, this adaptation resulting in covering the edge of the outer protrusion of the rim with a greater or lesser mass or protuberance of rubber of a suitable quality, the maximum axial width of the outer contour of the toe of the bead being greater than the space taken up or maximum axial width of the mounting rim.
Patent FR 2 779 386 teaches providing the axially outer protuberance of said bead with incisions of a width other than zero, of a depth at most equal to 5 mm and arranged circumferentially parallel to each other, which makes it possible to minimize the consequences of curb scrub on said axially outer protuberance of the bead, which is very sensitive on one hand to abrasion when the tire rubs against the curb, and on the other hand to rubber fragments being torn off following the initiation and propagation of cuts and/or tears.
In addition to the reduction in scrubbing between the outer wall of a protuberance owing to the presence of numerous thin rubber elements, it would appear that the propagation of the degradation of the rubber mass is minimized by this presence, which very clearly reduces the visual perception of the damage caused.
To minimize the phenomena of unwinding of the carcass reinforcement from around the annular reinforcement element of the bead heel, application FR 2 788 239, advocates a modification of the angle φ formed by the tangent TT′, to the point of tangency T of the meridian profile of the carcass reinforcement with the annular element of the bead, relative to the axis of rotation, said angle φ being between 45° and 70°. In the portion located in the bead zone, the greater inclination of the meridian profile of the carcass reinforcement also permits lesser degradation of the axially outer walls of the beads, in particular the beads placed to the outside of the vehicle fitted with such tires. However, this also involves many drawbacks in particular, a great reduction in the radial, transverse, and longitudinal rigidities, which is not without effects on the behavior of the vehicle.
To obtain a tire, destined to be mounted on a rim having at least one seat inclined towards the outside, having non-degraded rigidities while enabling the beads of the tire and the rim not to be damaged by the shocks and/or friction of all types, the invention proposes combining the meridian profile of the carcass reinforcement of tangent 45°–70° with a specific sidewall structure referred to as having an additional ring.